Method and apparatus for controlling operations of solvent-recovery plants



Aprii l3 1926. 1,580,157

G. G. OBERFELL METHOD AND APPARATUS FOR CONTROLLING OPERATIONS 0F SOLVENT RECOVERY PLANTS Filed April 18v 1925 2 SheetsSheet l M FIG.1:

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April 13 1926. 1,580,157

G. G. OBERFELL METHOD AND APPARATUS FOR CONTROLLING OPERATIONS OF SOLVENT RECOVERY PLANTS Patented Apr. 13, 1926.

UNITED STATES GEORGE G. OBERFELL, 0F TULSA, OKLAHOMA.

METHOD AND APPARATUS FOR CONTROLLING OPERATIONS OF SOLVENT-RECOVERY PLANTS.

Application filed April 18, 1925. Serial No. 24,047.

To all whom it may concern:

Be it known that I, Gnonon G. OBERFELL, a citizen of the United States of America, residing at Tulsa, in the county of Tulsa and State of Oklahoma, have invented certain new and useful Improvements in Methods and Apparatus for Controlling Operations of Solvent-Recovery Plants, of which the following is a specification.

This invention pertains to improvements in the methods and apparatus for conducting tests useful for the-control work in industrial plants employing absorption, d1s tillation, and rectification processes and is intended more especially for control work in natural gasoline plants, refineries, benzol recovery plants and in other industrial processes where problems of absorption, distillation, and fractionation are encountered.

A knowledge of the vapor pressure of a mixture of liquids is desirable in the control of absorption, distillation, and fractionation processes. Methods for determining vapor pressures of liquid mixtures of low vapor tension have been proposed, but these pro posed methods depend for the most part upon a direct measurement of the vapor pressure and employ the static vapor pressure principle. Owing to the low vapor pressures which obtain for most plant operations, the methods heretofore proposed are not adaptable for general plant control work. In addition, the solution of air in liquids whose vapor tensions are being determined frequently causes large errors in results of tests in ordinary static vapor pressure determinations.

The object of the present invention is to provide improved methods for the above mentioned problems and to furnish an apparatus which is readily and economically constructed and operated and is capable of producing accurate test results which are essential in plant control operations.

Other objects and advantages of the invention will be apparent during the course of the following description.

In the accompanying drawings forming a part of this specification and in which like numerals are employed to designate like parts throughout the same,

Figure 1 is a diagrammatical view of the apparatus embodying this invention when the same is completely assen'ibled and ready for performing a test of oils or other liquid mixtures,

Figure is a diagrammatic view of the rear of the panel shown in Fig. 1 for illustrating the instrumentalities located on the rear of this panel, and

Figure 3 is a fragmentary diagrammatic view of a portion of the apparatus shown in Fig. 1 as being associated with the panel and illustrates this portion of the apparatus when a test of gaseous mixtures is to be made. i

In the drawings, wherein for the pun pose of illustration is shown a preferred embodiment of this invention, the numeral 5 designatps a standard employed for supporting a panel or frame 6 upon the front side of which is removably mounted a vessel 7 adapted for receiving distilled water. Adj acent to this vessel is suitably mounted what will be generally termed a pipette 8 while next to the pipette 8 there is mounted a pipette 9. Submerged withinthe distilled water in the vessel 7 is an additional pipette 10 which is provided with a stem 11 having a scale line 11 suitably formed thereon. This stem 11 is coupled to what will be termed a stop-cock manifold 12 which has interposed therein a removable stop-cock 13 suitable for affording communication between the stem 11 and the manifold 12 or for providing communication with the at-' mosphere when the said stop-cock is removed.

The pipette 8 is provided with a blower 14 and a stem 15 havin a level scale line 15. This stem 15 is coup ed to the manifold 12 through the stop-cock structure 16 which is similar to the stop-cock 13. This pipette 8 is intended to use mercury as the confining liquid and is provided with the platinum spiral 17 which is electrically connected by the wires 18 to a source of electricity controlled by the switch 19 and the rheostat 20. The interior of this pipette 8 communicates with a pipe 21 which extends through the panel 6 and is connected to the leveling bottle 22 shown in Fig. 2.

The pipette 9 is intended of tubes 23 and caustic potash and is provided with a stem 24 having a level scale line 24 formed thereon and is coupled to the stop-cock structure 25 which is similar to the structures designated by the numeral to house a bundle 13 and 16 and which communicate with the stop-cock manifold 12. The lower end of this pipette 9 is provided with a stem 26 which has a branch 27 connected to a flexible tube 28 which leads to the compensating capillary tube 29 intended to be mounted adjacent to the pipette 9. This compensating capillary tube 29 is provided with a. level scale line 29 and is connected to the stopcock structure 30 which further communicates with an open nipple 31 which permits "the forming of a communication with the atmosphere. The stem 260i the pipette 9 is further connected to a flexible tube 32 which has its remaining end suitably connected to a stem 33 of a leveling bottle 34. This bottle is mounted orsupported within the ordinary burette clamp 35 and is adapted for being slidably adjusted in respect to the same.

A standard 36'is also provided and employs the adjustable brackets 37 for supporting the water jacket 38 which is intended to be supplied with distilled water and has its opposite ends closed by the'rubber stoppers 39. Entering this water jacket 38 is a compensating tube 40 which is intended to be supplied witha few cubic centimeters of distilled Water before being assembled. The presence of the water in this tube is intended to compensate for changes in aqueous tension. This tube 40 extends through the upper rubber stopper 39 and is connected to the stop-cock structure 30 by the tubing or piping 41. The water j acket 38 also has projecting therein the agitating tube 42 formed with the outwardly arranged portion 43 and having a suitable connection at. its end 44 to a source of air supply.

The water jacket 38 is further provided with the burette 45 which is graduated to .01 c. c. permitting readings as low as .002 c. c. This burette 45 is intended to use mercury as the confining liquid. The lower end of the burette is connected by the flexible tubing 46 to the leveling bottle 47 vertically adjustably supported by the standard 48. The upper end of the burette 45 communicates by means of the stem 49 with the stopcock structure 50 which is suitably connected by means of the piping 51 to the stop-cock manifold 12. s This stop-cock structure 50 is further provided with a pipe 52 which extends to the stop-cock structure 53 having a pipe connection 54 which opens to the atmosphe're and a pipe 55 formed with a goose neck 56 which extends into the vessel 57 adapted for receiving distilled water to the level indicated. The end 56' is intended to be passed into the bottle 58, when the apparatus is employed for testing samples of gaseous mixtures, which bottle contains the sample of gas. This vessel 57 is suitably supported by a standard 59.

With the exception of the water vessel 57,

the pipe 55, the goose neck 56 and the remaining elements associated therewith, the instrumentalities so far described are employed as shown in Fig. 1 for making tests of oils and other liquid mixtures. In employing'the apparatus for testing gaseous mixtures, the water vessel 7 and pipette 10 are dispensed with and the pipette 60 substituted in their place. This pipette 60 is intended to contain the pyro solution and the bundle of tubes 61 and has its stem 62 provided with the level scale line 62 and its stem 63 connected through the panel 6 to the leveling bottle 64 by means of the tubing 65, the bottle 64 being arranged on the rear face of the panel 6. This bottle 64 is intended to be connected in the manner illustrated to the inflatable bag 66. The remaining elements shown in Fig. 1 are employed in this test. The said stein 62 of the pipette 60 is suitably coupled to the stop-cock structure 13 to which the formerly described pipette 10 was coupled.

As has been suggested heretofore, this apparatus is capable of being used, with but minor changes, for the purpose of testing denuded oils and other liquid mixtures and, also, for testing gaseous mixtures. For this reason, the methods employed for testing oils and liquid mixtures will first be described and then a brief description of the inethod of testing gaseous mixtures will be given with the differences in the two different types of tests pointed out.

Testing denuded oils and other liquid mixtures.

Taking oz'Z sampZe.-As in any method of testing, the sample to be tested should be taken at a time, and over a period of time long enough to insure a representative analysis. The oil sample should be collected over water. This may be done by inverting a bottle filled with water in a bucket of water and by means of a piece of rubber tubing or small pipe introduce the oil into the bottle. The bottle is then stoppered while under water. Care should be taken that the sample to be tested vis not contaminated. For example, if the oil is taken just before it enters the absorber, a leaky heat exchanger would cause erroneous results. For this reason it is advisable to take the sample of denuded oil at a place in the line between the still and heat exchanger and thereby avoid possibility of error from this source.

Procedure of area'ysis.There are two distinct methods which may be followed in testing oil samples. One method consists in determining the increase that occurs when a definite volume of air is brought into contact with the oil. This increase in volume of air is due to the gasoline which evaporates from the oil thereby saturating the air with gasoline vapor and causing an increase in volume equal to the volume of gasoline vapors liberated from the oil. The second method which can be used as an independent check on the former method consists in burning the gasoline vapor air mixture, obtained in the former method. The shrinkage in gas volume due to combustion and the carbon dioxide produced thereby atford a means of calculation of the volume of gasoline vapor present in the gaseous mixture. The arrangement of apparatus used in conducting the 'e tests is shown in Figs. 1 and 2. Before introducing the oil sample into the pipette 10, cool the oil sample to approximately 32 1 then by means of a sampling pipette, not shown, remove approximately 25 c. c. from the sample bottle and immediately replace the stopper in the sample bottle. Introduce the oil in the sampling pipette into the pipette 10 through the opening 10 near the bottom of this pipette 10.

Oil samples should not be exposed to the air for a longer period of time than that necessitated in removing the sample, since the ezcape of gasoline from the oil leads to low test results. \Vhere'conditions warrant, samples can be removed from the sample bottle and introduced into the pipette to by water displacement. However. the former method is quite satisfactory for ordinary routine work.

After introducing the oil sample into the pipette 10 the distilled water in the \csi'el 7 is brought to the desired temperature and kept constant during the entire analysis by the expansion method. This water bath temperature should be the same as the ab- .OI'PllOIl temperature at the plant at which the sample was taken. For the. purpose of comparing results of tests of oils taken under ditl'erent operating coi'nlition.-=. a .stttiltltlltl temperature of 70 1*. has been employed and tests made at this temperature in addition to the plant absorption temperature.

knowing the results of tests at one tcn1 perature. the results of tests for other temperatures may be calculated ili' (llr ll'Ctl. However, the assumptions upon which calculations are based do not justify such calculations for-general work. considering the readiness and'case with which actual dcterminations may be made. 1

Before beginning the analysis. cause air to bubble through the distilled water in the jacket 38. and then open stopcock :30. While raising the leveling bottle lT. so that communication is atlorded between the burette -15 and the air or atmosphere surrounding the apparatus. Next raise the leveling bottle 47 until the mercury in the burette '15 rises to the end of the pipe 54 open to the atmosphere. lower the leveling bottle 4T. at the same time introduce a few c. c. of water into the burette 45 through pipe (it by any of several well known means, such as, by means of a funnel and rubber tubing with the latter connected to the point of entry. The purpose of introducing water into the burette is to compensate for an error that woud be introduced during the analysis due to the change in aqueous tension. Then allow the mercury in-the burette to to recede slowly until it falls to the c. c. mark on the hurette. Raise the leveling bulb atT slowly until the mercury begins to flow from the open end of the pipe :"i-l. Remove the water which adheres at the end of the pipe 54: by means of a blotter. Repeat the operation of raising and lowering the leveling bottle d6 a few times so as to remove all visible Water from the surtac of the mercury in the burette-45. This alternate raising and lowering the leveling bottle 47 is necessary to make sure that no appreciable amount of water over that required to saturate the gas remains in the burette. It a large amount of water were left in the burette it would introduce errors in reading the volume of gas. Enough water clings to the walls of the burette and to the. mercury so that the gas during analysis will be saturated with water vapor. Calculations based on molal volume and vapor pressures of water show that 0.005 c. c. of water in the liquid form will completely saturate gas used for analysis in a dozen or more tests. Practical experience with the operation of the apparatus shows that themethod recommended is entirely adequate. Finally lower the leveling bottle iT until the mercury-level in the burette rests at about the 20 c. c. markwhile the stop cook .30 is still open to the air. Adjust the level of liquid in the con'ipensating capillary tube 29 to the level scale line 2t) by means of the leveling bottle 3 The stop cock should then be closed and the stop cock 50 turned to afford communication with the manifold 12. Raise the leveling bottle -tT about one inch orto a height l'ound necessary in practice to prevent drawing liquid into the manil'old 12. The stop-cock 25 should then be open. Adjust the levelsoi" the liquids in the burette Q and the compensating tube 29 to the levels 94 and 20 respectively and read and record the exact volume of air enclosed tor the analysis. lie sure to check the liquids at the levels 24' and 25) immediately after reading to see that they did not change during the reading of the burette 4-5. liaise the leveling bottle 'ti and thereby torcc gzu into thcpipcttc t). l'ass this gas rcpcattally. say live or six times. from the burette if to the pipette ti allowing the sample to remain in contact with the caustic potash in the pictlc 3 about til'tcen seconds each passage. Then return the air to the burette 45. and with the stop-cock 2.3 open as bct'orc restore the liquids to the levels it and it) by adjustment ot' the leveling bottles H and 3- Read the record volume, observingprecautions as previously instructed. 'The shrinkage in gas volume obtained by the operation represents the volume of carbon dioxide present in the'sample and which has been removed by the caustic. Repeat the operation of passing the gas into the caustic and again read and record the volume as above. If a check within .002 c. c. is obtained on this reading it means that all of the carbon dioxide has been removed. If a check reading has not been obtained, repeat absorption in the caustic solution in the pipette 9 until duplicate readings are obtained. Failure to obtain check readings after the first few trials generally indicates a leak in the apparatus.

After obtaining duplicate readings, ascertain that the distilled water bath in the vessel 7 is at a proper temperature. Close the stop-cock 25, raise the leveling bottle 47 a few inches, open the stop-cock 13, and then pass the gas sample from the burette 45 into the pipette 10 by raising the leveling bottle 47. Repeat this operation as in the case of carbon dioxide absorption with the exception that the sample is allowed to remain in contact with the oil for a full twenty seconds during each passage. Return the air sample which is now enriched with gasoline vapor to the burette 45, restoring the level in the pipette 10 to the scale line 11". Close the stop-cock 13, raise the leveling bottle 47 slightly to a height found necessary in practice to prevent drawing caustic potash into the manifold 12 and thenopen the stop-cock 25. Adjust the levels of the liquids in the pipette 9 and compensating tube 29 to the scale lines 24 and 29, read and record the volume of gasoline vaporair mixture. The increase in volume over previous reading represents the amount of gasoline vapor removed from the oil. Repeat the operation of contacting air sample with the oil until no further increase in the volume of air occurs, being sure to maintain a constant temperature in the water bath in the vessel 7 during this entire operation. A constant water level must be ,had in the vessel 7 before adjustments are made prior to-reading the burette 45. After obtaining duplicate readings, close the stopcock 25, open the stop-cock 16 and raise the leveling bottle 47 until the mercury in the pipette 8 falls below the platinum spiral 17. The blower 14 should then be started and the switch ltlturned to its circuit closing position. The function of the blower 14 is to keep the combination pipette 8 cool during combustion and prevent same from breaking due tocxcessive heat, which would occur if the pipette were not kept cool. The heat on the platinum spiral 17 may be adjusted by the rheostat 20 until the wire has a bright yellow appearance, a white heat causing the wire to be burned out. It is desirable not to pass the entire gas sample into the pipette 8 since with explosive mixtures, the force of explosion might cause damage or leaky connections if the entire sample is ignited. Raise the leveling bottle 47 slowly until the gas from the burette 45 has been passed into the pipette 8. Then pass the gas backward and forward about ten. times, but in this operation do not return enough of the sample so as to allow n'iercury in the pipette 8 to rise above the glass terminals to which the platinum spiral is attached. 1n passing the sample between the burette 45 and the pipette 8, allow a tull sample to remain in the pipe 8 between each passage for about fifteen seconds. Turn oil the switch 19 and allow the combustion pipette 8 to cool for a few minutes. When the glass of this pipette is only 'perceptibly warm to the hand, the blower 14 should be turned otf and the sample returned to the burette 45, after which the mercury in the pipette 8 should be returned to the level 15 and the stop-cock 16 closed. Again read and record the volume of sample observing instructions and recautions as in other readings. The shrin 'age or contraction in gas volume is caused by combustion of the gasoline vapor. Since carbon dioxide is formed by. combustion of the gasoline vapor, the carbon dioxide must be removed. The procedure has been given above for this operation. F ollow the same procedure with the exception that only one reading need be obtained at this time. Bepeat the combustion and the absorption of carbon dioxide until no further dimunition in volume occurs, being sure. to record one reading for each combustion and absorption.

Taking .m-1np7c.'lhe usual method of collecting gas samples is by water displacement. in a manner similar to that used for securing salnplcs of oil. For most work this method is satisfactory. The arrangement of the apparatus whereby the gas samplc is introduced into the burette 45 for analysis is shown in the various figures and it is to be understood that the panel (3 now has the elements illustrated in Fig. 3 arranged thereupon.

Procedure for unaZ z .sia.-'ll1e procedure for analysis of gaseous mixtures is very similar to that described above for testing oils. However, the following additional precautions should be observed.

In analyzing a gas sample. it is best to store it over mercury, although water may be used it limits of accuracy permit such a procedure. If the sample is to be taken into the burette 45, the goose neck 56 should be filled with mercury before a connection is made in order to prevent contamination of the gas sample with the air in 'the goose neck.

After inserting the goose neck 56 into the mouth of the bottle 58, place a linger or other temporary closure over the open end of the pipe 54, and turn the stop-cocks 50 and 53 so as to attord a communication be tween the burette 45 and the air through the pipe 54. Raise the leveling bottle 47 and expel samples of gas from the burette 45 into the room. Turn the stop-cock 52-} so that communication is afforded between the burette 45 and the sample of gas in the bottle 58. Lower the leveling bottle 47 and draw gas from the bottle 58 into the bure'tte 45. The first few samples should be discarded so as to eliminate contamination of the sample with air in the connection between the burette and the sample bottle 58. Finally, draw a sample of about twenty c. 0. into the burette 45, close the stop-cock 53 and turn the stop-cock 50 so as to close communication between the bottle 58 and the burette 45.

In drawing samples into the burette, sometimes a reduced and sometimes an increased pressure is obtained on gas within the burette. Observe whether the surfaces of mercury in the burette 45 and the leveling bottle 47 appear to be on approximately the same level. Adjust the leveling bottle 47 so that the mercury level therein is slightly above that in, the burette'.

The stop-cock 30 should then be turned to afford communication with the air through the nipple 31. Bring the level of the caustic potash in thecompensating capillary tube 29 up to the scale line 29, close the stopcock 30, open the stop-cock 49, and then the stop-cock 25 and proceed as instructed for analysis of oil sample with the exception that the analysis is first made for carbon dioxide content and then for amount of combustible gas present in the mixture. As stated above, for the gas analysis, the pipette 10 and the vessel 7 are replaced by the pipette 60, see Fig. 3, which contains the pyro solution which is used to remove the oxygen from the gaseous mixture. After determining the carbon dioxide and combustibles, the sample of gas remaining is analyzed for oxygen by passing it into the pipette 60, if it is desired to make calculations for three combustible constituents. If combustibles are found to be present, it is advisable generally to make an analysis of oxygencontent on a separate sample of the gas. This procedure is of course necessary if three combustible components are present in the mixture, since it is necessary to know the amount of oxygen consumed during combustion.

It is now believed that the manner of arranging the various instrumentalities embodving this apparatus and the method of utilizing thesame for producing the differcnt tests just described is to be' understood from the above detail description and that no further explanation is deemed necessary. It is to be understood that the form of the apparatus and the methods of testing as shown and described in connection with this invention are to be taken as preferred examples oi the same. and that various changes may be made without departing front the spirit ottbe invention or the scope of the subjoined claims.

Having thus described the invention, I claim l. A method of determining the vapor pressure of liquid mixtures which consists in contacting a definite volume of air with the liquid mixture and determining the volumetric increase in the volume of air due to its saturation with vapor from the liquid mixture. v

2. A method of determining the vapor pressure of liquid mixtures which consists in contacting a definite volume of air with the liquid mixture and determining the volumetric increase in the volume of air due to its saturation with vapor from the liquid mixture, subjecting the vapor air mixture to combustion, which results in the formation of carbon dioxide and water accompanied by a. shrinkage in gas volume, and then re moving the carbon dioxide by contacting it with a caustic solution.

3. A method of determining the vapor PIUSEHICS'Of liquid mixtures which consists in measuring a definite quantity of air, saturating the air with vapor from the liquid mixture for causing a volumetric increase in the quantity of air to indicate the saturation of the liquid mixture with vapor, extracting thevapor from the quantity of air by burning the vapor which results in the formation of carbon dioxide and water accompanied by a shrinkage in gas volume, and removing the carbon dioxide by contacting it with caustic potash.

4. An apparatus of the class described comprising means'for measuring a definite quantity of air, means for holding a sample of liquid mixture, and means for passing afquantity of air into and out of the said sample holding means.

5. An apparatus of comprising means for quantity of air, means of a liquid mixture, a liquid bath for said sample holding means, and means for passing the aforesaid quantity of air into and out of the said sample holdingmeans.

6. An apparatus of the class described comprising a graduated tube tor measuring a definite quantity of air, a liquid bath, .a pipette for holding a sample of liquld mixture in said bath, a connection between the the class described measurlng a definite for holding a sample tube and the pipette, and means for passin the quantity of air into and out of the pipette.

7. An apparatus of the class described comprising a graduated tube for measuring a definite quantity of air, a liquid bath, a pipette for holding;' a sample of liquid mixture in said bath, a connection between the tube and the pipette, a combustion pipette communicat'ing with the said connection, and means for passing the quantity of air into and out of the first mentioned pipette.

8. An apparatus of the type described comprising a graduated tube for measuring a definite quantity of air, a liquid bath, a pipette for holding a sample of liquid mixture in said bath, a connection between the tube and the pipette, a combustion pipette communicating with the said connection, a pipette containing caustic potash communicating with the said connection, and means for passing the quantity of air into and out of the said pipettes.

In testimony whereof I alfix my signature.

GEORGE (l. OBERFELL. 

